As representative consumable electrode-type arc welding methods, there are pulse welding and short-circuit welding, which have been put to practical use. However, the pulse welding and the short-circuit welding have problems as follows.
The pulse welding has lower heat-input than a spray shift in a constant current exceeding a critical current. However, since an arc length which is long to a certain degree is required to maintain a stable pulse shift, it is not possible to reduce heat-input. Therefore, in so-called position welding, such as vertical welding and overhead welding, a bead, such as a sagging bead, having an unpreferable shape is likely to be generated.
In the short-circuit welding, the arc length is short, and welding defect, such as incomplete fusion, is likely to occur during a short-circuit period since heat-input related to the arc is small. Moreover, sputter is often generated due to the short arc length and short circuit.
To prevent the above-described problems, an arc welding method in which the pulse welding and the short-circuit welding are controlled as to be alternately repeated a predetermined number of times has been proposed (refer to PTL 1). FIG. 4 illustrates a waveform of a welding current when arc welding is controlled in conventional arc welding disclosed in PTL 1. The welding current is controlled such that the pulse welding and the short-circuit welding are alternately performed a predetermined number of times. A welding wire is fed at a constant feeding velocity so as to obtain an optimal value in each of the pulse welding and the short-circuit welding. PTL 1 discloses that welding defect, such as incomplete fusion, or a bead having an unfavorable shape, such as a sagging bead, in position welding can thereby be prevented from occurring by controlling the heat-input and controlling the shape of the bead.
As a method of reliably preventing generation of sputter and performing a short circuit shift in the short-circuit welding, a welding method in which generation of an arc and short circuit is detected, a welding wire is fed (fed forward) in response to generation of an arc and the wire is pulled up (fed backward) in response to generation of short circuit is disclosed (refer to PTL 2).